Place Dutch oven over medium heat and melt butter and oil together.
Add onion, carrot, celery, and garlic and season with salt and pepper. Sauté together until onions become translucent and vegetables soften, about 8 minutes.
Add ground beef, pork and sausage and break up using a wooden spoon. Season with salt and pepper.
Cook mixture together, while stirring frequently, until meat loses its raw color, about 5 minutes.
Add nutmeg and milk and stir together. Simmer until milk reduces by 50%, about 10 minutes.
Stir in canned tomatoes, including juices, and break tomatoes up with wooden spoon. Season with salt and pepper.
Lower heat to medium-low and simmer sauce for about 1 1/2 hours, occasionally stirring. If sauce becomes too dry, add ½ cup water and stir together.
Adjust salt and pepper as needed and serve sauce with pasta of choice.